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A chordate (/ ˈ k ɔːr d eɪ t / KOR-dayt) is a deuterostomal bilaterian animal belonging to the phylum Chordata (/ k ɔːr ˈ d eɪ t ə / kor-DAY-tə). All chordates possess, at some point during their larval or adult stages, five distinctive physical characteristics ( synapomorphies ) that distinguish them from other taxa .
This article contains a list of all of the classes and orders that are located in the Phylum Chordata. The subphyla Tunicata and Vertebrata are in the unranked Olfactores clade, while the subphylum Cephalochordata is not. Animals in Olfactores are characterized as having a more advanced olfactory system than animals not in it.
Pikaia gracilens is an extinct, primitive chordate marine animal known from the Middle Cambrian Burgess Shale of British Columbia.Described in 1911 by Charles Doolittle Walcott as an annelid, and in 1979 by Harry B. Whittington and Simon Conway Morris as a chordate, it became "the most famous early chordate fossil", [1] or "famously known as the earliest described Cambrian chordate". [2]
Harvard University palaeontologist Stephen Jay Gould popularised Pikaia as an ancestral species of chordates in his 1989 book Wonderful Life: The Burgess Shale and the Nature of History, [13] from which Pikaia became known as the "most famous early chordate fossil," [14] or the earliest chordate, [15] or the oldest ancestor of humans. [16] [17]
The notochord is also toward the tail of the chordate but closer toward the middle of the body than the dorsal nerve cord and is a water-filled structure that allows the chordate to move in water. [3] The endostyle is underneath the pharyngeal gill slits where proteins are trapped to eventually provide the chordate energy and sustenance. Lastly ...
Early screens to identify genes involved in cuticle development led to the discovery of a class of genes that was necessary for proper segmentation of the Drosophila embryo. [ 3 ] To properly segment the Drosophila embryo, the anterior - posterior axis is defined by maternally supplied transcripts giving rise to gradients of these proteins.
Agnatha (/ ˈ æ ɡ n ə θ ə, æ ɡ ˈ n eɪ θ ə /; [3] from Ancient Greek ἀ-(a-) 'without' and γνάθος (gnáthos) 'jaws') is a paraphyletic infraphylum [4] of non-gnathostome vertebrates, or jawless fish, in the phylum Chordata, subphylum Vertebrata, consisting of both living (cyclostomes) and extinct (conodonts, anaspids, and ostracoderms, among others).
A craniate is a member of the Craniata (sometimes called the Craniota), a proposed clade of chordate animals with a skull of hard bone or cartilage.Living representatives are the Myxini (hagfishes), Hyperoartia (including lampreys), and the much more numerous Gnathostomata (jawed vertebrates).